1916] Gilkeij: A Revision of the Tuherales of CaJiforuia 809 



Tuber Mich. 



Aseocarp regularly globose to very irregular, fleshy or cartilagin- 

 ous ; surface smooth, verrucose, or with coarse projections ; cortical 

 tissue often pseudoparencliyniatous ; subcortex of laterally extending 

 hyphae, loosely arranged or more or less united ; gleba penetrated by 

 venae externae and venae internae (latter rarely wanting) ; venae 

 externae filled with hyphae, opening at various points of surface, or 

 converging more or less distinctly at one i^oint oi- line or several points 

 or lines : venae internae originating from subcortex, lying usually 

 parallel with veiuie externae, composed of generally parallel hyphae, 

 loosely arranged or more or less united, sometimes pseudoparen- 

 ehynuitous ; hymenium lying between two vein systems, consisting of 

 irregularly arranged asei separated by strands of tissue generally 

 similar in structure to that of venae internae ; asci usually nunierous, 

 pyriform, ellipsoid or nearly globose, with 1 to 4 or more spores, num- 

 ber varying in asci of single aseocarp, size of spore varying with inun- 

 ber in ascus : spores ellipsoid or globose, alveolate or spiny, irregu- 

 larly arranged in ascus. 



The genus Tuhcr is generally divided into two subgenera: Eiitnher. 

 with the venae externae opening at various points of the surface, and 

 the consistency of the aseocarp generally fleshy; and Aschion, with 

 the venae externae converging and opening at the base of the aseocarp, 

 the consistency of the latter being hard, horny, or woody. No plants 

 of the true Aschion type have yet been reported from California, but 

 it is approached by Tuber candid um and T. lignarium, both having a 

 somewhat cartilaginous aseocarp with venae externae converging and 

 opening to the surface along a definite line or point or several con- 

 nected or separated lines or points. These lines are somewhat irregu- 

 larly arranged, sometimes occurring singly on one side of the aseocarp, 

 but often extending half the distance around it, and more or less 

 branched, or joined by other lines. 



Sometimes there are a number of short lines, or occasionally several 

 of these are reduced to points, and in these cases there are as many 

 "centers" of converging venae externae. There is no definite orienta- 

 tion of llic plant in relation to these lines, for they iiui\' be fouii<l upon 

 the upper surface or a side of the aseocarp as often as at the base. 



According to the sculpturing and shape of the spores, Tuher species 

 have been divided into four groups: Eutnhcr, including those with 

 ellipsoid, alveolate spores; Sphaerotuher, with globose, alveolate 

 spores; Oogaster, with ellipsoid, spinose spores; and Sphaerogaster, 

 with globose, spinose spores. By far the greater number of Call- 



